My apps are getting rejected on store and the defect given is “Application does not provide valuable, entertaining, unique and/or informative uses.”

My apps are about recipes, convertors and calculators. I don’t know why they are approving tips related apps of my friends and rejecting my apps with better functionality than them.

Content Ids of some my apps are as follows :

Love Calculator                    54612

Speed Convertor                  54304

Pressure Convertor              54296

ChickenTetrazzinni              54286

BlueberryCornMuffins         54282

And one of my app earlier got certify and validated and after few days it was suspended from store due to default author certificate used. I updated my app with new author certificate and submitted the app again. Now it got rejected and reason is “Application does not provide valuable, entertaining, unique and/or informative uses.”

FA Calculator       54305

Please guide me why this is happening while I have simillar apps published on various platforms like WindowsPhone Marketplace, Windows Marketplace, BlackBerry Store etc. and here they are getting rejected.